1. Field of the Invention
The present invention relates to an information storage device, and more particularly, to a disk spacer, which is interposed between disks for an information storage device to maintain a predetermined interval between the disks, and a spindle motor assembly employing the disk spacer.
2. Description of the Related Art
Apparatuses that store information in computers, such as hard disk drives (HDDs) and optical disk drives (ODDs), record data on a rotating disk that is mounted around a spindle motor, or reproduce data recorded on the rotating disk.
FIG. 1 is a schematic exploded perspective view of a conventional HDD. Referring to FIG. 1, a spindle motor 30 for rotating an upper disk 21 and a lower disk 22, which act as mediums for recording and storing data, and an actuator 40 for moving a read/write head, which reproduces and records data, to a desired position on a disk 20 are mounted on a base member 11 of an HDD.
The spindle motor 30 is mounted on the base member 11. The two disks 21 and 22 may be mounted around the spindle motor 30 as shown in FIG. 1, and one, or three or more disks may be mounted around the spindle motor 30 as well. If a plurality of disks, e.g., two disks 21 and 22 are mounted around the spindle motor 30, a spacer 50 having a ring shape is interposed between the disks 21 and 22 to maintain a predetermined interval between the disks 21 and 22. A clamp 60 is screwed to an upper end portion of the spindle motor 30 with a screw 70 to firmly fix the disks 21 and 22 to the spindle motor 30.
The actuator 40 includes a swing arm 42, which is rotatably coupled to a pivot 41 that is installed on the base member 11, a suspension 43, which is installed on one end portion of the swing arm 42 and elastically biases a slider with the head thereon toward surfaces of the disks 21 and 22, and a voice coil motor (VCM) 45, which rotates the swing arm 42. The VCM 45 is controlled by a servo control system, and rotates the swing arm 42 in a direction according to Fleming's Left Hand Rule due to an interaction between current input to a VCM coil and a magnetic field generated by magnets. That is, if the disk drive is turned on and the disks 21 and 22 begin to rotate, the VCM 45 rotates the swing arm 42 counterclockwise to move the head over the recording surfaces of the disks 21 and 22. On the other hand, if the disk drive is turned off and the disks 21 and 22 stop rotating, the VCM 45 rotates the swing arm 42 clockwise to remove the head from the recording surfaces of the disks 21 and 22. The head removed from the recording surfaces of the disks 21 and 22 is parked on a ramp 46 disposed outside the disks 21 and 22.
A cover member 12 is secured to the base member 11 with a plurality of screws 19. The base member 11 and the cover member 12 secured to the base member 11 collectively enclose and protect the disks 21 and 22, the spindle motor 30, the actuator 40, and so on.
A combination of the spindle motor 30, the disks 21 and 22, the spacer 50, and the clamp 60 will be explained in further detail with reference to FIG. 2.
Referring to FIG. 2, the spindle motor 30 includes a shaft 31 fixedly installed on the base member 11, and a stator 33 and a rotator 34, which are mounted around an outer periphery of the shaft 31. The rotator 34 is called a hub. The disks 21 and 22 for data storage are mounted around an outer periphery of the hub 34. As described previously, if the plurality of disks 21 and 22 are mounted around the spindle motor 30, the ring-shaped spacer 50 is mounted around the outer periphery of the hub 34 to be interposed between the disks 21 and 22 so that the spacer 50 can maintain a predetermined interval between the disks 21 and 22. Then, the clamp 60 for fixing the disks 21 and 22 is screwed to an upper end portion of the shaft 31 with the screw 70.
In the HDD constructed as above, data recording and reproducing is performed by the read/write head, which flies over the rapidly rotating disks 21 and 22 at a very small height. If impacts are applied to the HDD, the impacts are delivered to the disks 21 and 22 through the base member 11, the shaft 31 of the spindle motor 30, the shaft screw 70, and the spacer 50. Vibrations caused due to the rotation of the spindle motor 30 are also delivered to the disks 21 and 22 through the shaft 32, the shaft screw 70, the clamp 60, and the spacer 50. The impacts and vibrations delivered to the disks 21 and 22 cause the disks 21 and 22 to wobble, and accordingly, the disks 21 and 22 collide with the head, thereby damaging the surfaces of the disks 21 and 22 and the head. Further, the wobble of the disks deteriorate the function of the read/write head.
In particular, in the conventional HDD, since the spacer 50 interposed between the disks 21 and 23 has a rectangular section, the impacts or vibrations delivered from the clamp 60 to the upper disk 22 are delivered to the lower disk 21 through the spacer 50, as shown by arrows in FIG. 2. That is, the conventional disk spacer 50 having a rectangular shape cannot lessen impacts or vibrations.
In the meantime, FIG. 3 is a sectional view of a disk spacer having a -shaped section disclosed in Japanese Patent Laid-Open Publication No. hei 9-115216.
Referring to FIG. 3, a plurality of disks, for example, two disks 81 and 82, a spacer 85, and a clamp ring 84 are mounted around an outer periphery of a motor hub 83. The clamp ring 84 is inserted into a recess 87, which is formed on an outer peripheral surface of the motor hub 83. A spacer groove 86 is formed on an outer peripheral surface of the spacer 85, and the spacer groove 86 has a rectangular section. Consequently, the spacer 85 has a -shaped section.
According to the conventional spacer 85, an upper projection and a lower projection of the spacer 85, which are formed by the spacer groove 86, act as springs, such that a pressure applied to the disks 81 and 82 is uniformly distributed to the disks 81 and 82 due to the clamp ring 84. However, if impacts or vibrations are applied to the spindle motor, the impacts or vibrations are reflected by the upper projection of the spacer 85, and affect the upper disk 82 again.
For example, the wobble of disks due to impacts under the same conditions was simulated. When the spacer illustrated in FIG. 2 was interposed between disks, the maximum displacement at edge portions of the disks due to the impacts was approximately 1.0 μm, and when the spacer illustrated in FIG. 3 was interposed between disks, the maximum displacement at edge portions of the disks was approximately 1.06 μm. It can be seen from the simulation results that the spacer having the □-shaped section shown in FIG. 3 fails to lessen the wobble of the disks caused by impacts or vibrations.